Printing data encryption protection method for printing equipment
By building a printing behavior estimate model and using hierarchical encryption technology, the problem of insufficient data encryption protection in traditional printing equipment is solved, and the secure transmission and storage of print data is realized, which enhances information security and data transmission efficiency.
Patent Information
- Application Number
- CN202510248910.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-04
- Publication Date
- 2025-06-24
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Traditional printing equipment lacks an effective data encryption protection mechanism, which leads to the security risks of printing data during transmission and storage, and may be intercepted, tampered with or stolen by unauthorized personnel.
A printing behavior prediction model is constructed, and the printing behavior data timing sequence between the user equipment end and the printing device end is matched by similarity, to determine whether printing tasks are allowed to be sent, and high or low importance encryption is performed according to the importance level of the printing task. At the same time, the preset network security protocol builds an encrypted communication channel and stores log information through the log database to support security analysis.
It realizes effective encryption protection for printed data, prevents unauthorized data access and tampering, enhances information security, and improves the security and efficiency of data transmission through exception detection and hierarchical encryption.
Smart Images
Figure CN120196291A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of data encryption, and specifically to a method for encrypting and protecting print data for a printing device. Background Art
[0002] In the current printing environment, printing devices are widely used in various office places, homes, and industrial fields. However, during the process of printing data being transmitted from the user device to the printing device and stored in the printing device, there are many security risks. Traditional printing devices often lack an effective data encryption protection mechanism, resulting in the possibility that print data may be intercepted, tampered with, or stolen by unauthorized personnel, posing serious information security risks to users and enterprises. For example, in an office network environment, malicious attackers can use network vulnerabilities to obtain the content of print tasks, thereby leaking important information such as business secrets and personal privacy; at the same time, in a public printing place, unprinted data stored in the printing device may also be illegally obtained by others. Therefore, developing a reliable method for encrypting and protecting print data has important practical significance. Summary of the Invention
[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a method for encrypting and protecting print data for a printing device, including the following steps:
[0004] Step s1: Construct a print behavior prediction model. When the user device sends a print task to the printing device, perform similarity matching between the time series of print behavior data between the user device and the printing device and the predicted time series of print behavior data output by the print behavior prediction model;
[0005] Step s2: When the similarity matching result allows the user device to send a print task, obtain the digest information of the print task, obtain the importance level corresponding to the print task according to the digest information, and perform high-importance encryption or low-importance encryption of the print data according to the importance level corresponding to the print task;
[0006] Step s3: Decrypt the data packet received by the printing device terminal, and perform data printing operations or generate a data tampering alarm signal according to the decryption result.
[0007] Further, preset a network security protocol (such as the SSL / TLS protocol, etc.), construct an encrypted communication channel between a number of user devices and the printing device according to the network security protocol, and construct a log database, where the log database is used to store the log information between the user device and the printing device.
[0008] Further, the process of constructing the print behavior prediction model includes:
[0009] Build a printing behavior prediction model based on deep learning, extract features from the log information in the log database, and obtain the time series of printing behavior data. The time series of printing behavior data includes various types of behavior metrics as follows: the creation time, sending time, receiving time, decryption time, printing start time, printing end time, summary information of the printed data, user identity information, encryption algorithm used, and key information. Use the printed data as the training set and the test set, input the training set into the printing behavior prediction model for training until the loss function is trained stably, save the model parameters, test the printing behavior prediction model through the test set until it meets the preset requirements, and output the printing behavior prediction model.
[0010] Building a printing behavior prediction model based on deep learning is a complex process that involves multiple steps such as model selection, training, validation, and testing. The following is a detailed supplementary description of this process:
[0011] The present invention selects a recurrent neural network (RNN) suitable for time series analysis as the deep learning architecture. After determining the model architecture, the mean squared error (MSE) is selected as the optimization objective, and then the prepared training set is input into the selected deep learning model to start training. During the training process, the weights are continuously updated through the backpropagation algorithm, making the loss function gradually decrease until it reaches a stable state. During this period, techniques such as Early Stopping are used to avoid overfitting. In addition to the basic training process, the various parameters of the model are tuned through Grid Search. The parameters include the learning rate, batch size, regularization coefficient, etc.
[0012] When the model training is completed and the parameters are adjusted, the final evaluation is carried out through the test set to obtain the evaluation results of the model. The evaluation results include classification metrics such as accuracy, recall rate, F1 score, etc. According to the evaluation results on the test set, it is judged whether the model meets the expected standards. If the requirements are met, the model parameters are saved and preparation for deployment is made; if not ideal, it is necessary to return to a previous stage to re-examine issues such as data quality, model structure, or training strategy.
[0013] Furthermore, when the user device sends a printing task to the printing device, the process of performing similarity matching between the time series of printing behavior data between the user device and the printing device and the predicted time series of printing behavior data output by the printing behavior prediction model includes:
[0014] A preset collection period, with the duration of the collection period being one day. Obtain the log information between the user device side and the printing device side during the current collection period, extract features from the log information, obtain the time series sequence of printing behavior data between the user device side and the printing device side, and according to the printing behavior prediction model, output the predicted time series sequence of printing behavior data between the user device side and the printing device side during the current collection period;
[0015] Perform similarity matching between the time series sequence of printing behavior data between the user device side and the printing device side and the corresponding predicted time series sequence of printing behavior data to obtain the printing behavior similarity. Compare the printing behavior similarity with the preset printing behavior similarity threshold. If the printing behavior similarity is greater than or equal to the printing similarity threshold, allow the user device side to send a printing task to the printing device side;
[0016] Among them, the calculation formula for obtaining the printing behavior similarity is:
[0017]
[0018] Among them, ds represents the printing behavior similarity, D iqt represents the value of the behavior index q at the t-th moment in the time series sequence of printing behavior data, D jqt represents the value of the behavior index q at the t-th moment in the predicted time series sequence of printing behavior data, n1 represents the total number of behavior indexes, and n2 represents the total number of moments within the collection period;
[0019] If the printing behavior similarity is less than the printing similarity threshold, reject the printing task sent by the user device side to the printing device side, generate a printing behavior anomaly alarm signal, send the printing behavior anomaly alarm signal to the administrator or user by means of email, text message or system pop-up window, and record the detailed information of the abnormal event for subsequent security analysis and processing.
[0020] Furthermore, obtain the summary information of the printing task, obtain the importance level corresponding to the printing task according to the summary information, and the process of performing high-importance encryption or low-importance encryption on the printing data according to the importance level corresponding to the printing task includes:
[0021] When allowing the user device side to send a printing task, extract the summary information of the printing task to obtain the summary information of the printing task. Preset the importance levels corresponding to different summary information, and the importance levels include high-importance level and low-importance level. Obtain the importance level corresponding to the printing task;
[0022] If the importance level corresponding to the printing task is the high-importance level, perform high-importance encryption on the printing data. If the importance level corresponding to the printing task is the low-importance level, perform low-importance encryption on the printing data.
[0023] Further, the process of performing low-importance encryption on print data includes:
[0024] Using a symmetric encryption algorithm, the user device generates a temporary symmetric key, uses the temporary symmetric key to encrypt the print task data to generate ciphertext print data, applies a hash function to the ciphertext print data to generate a hash value of the ciphertext print data, uses the temporary symmetric key to encrypt the hash value of the ciphertext print data to generate a digital signature of the ciphertext print data, packs the ciphertext print data, the digital signature, and the temporary symmetric key into a data packet, marks the data packet as a low-importance data packet, and sends it to the print device terminal.
[0025] Further, the process of performing high-importance encryption on print data includes:
[0026] Previously, use an asymmetric encryption algorithm to generate an asymmetric key pair for the user device, the asymmetric key pair includes a public key and a private key, and use a symmetric encryption algorithm to generate a temporary symmetric key for the user device, encrypt the print task data through the temporary symmetric key to generate ciphertext print data, apply a hash function to the ciphertext print data to generate a hash value of the ciphertext print data, use the temporary symmetric key to encrypt the hash value of the ciphertext print data to generate a digital signature of the ciphertext print data, encrypt the temporary symmetric key through the private key to generate an encrypted symmetric key, pack the ciphertext print data, the encrypted symmetric key, and the digital signature into a data packet, and mark the data packet as a high-importance data packet and send it to the print device terminal.
[0027] Further, the process of decrypting the data packet received by the print device terminal and performing a data printing operation or generating a data tampering alarm signal according to the decryption result includes:
[0028] When the print device terminal receives a low-importance data packet, decrypt the ciphertext data through the temporary symmetric key to obtain decrypted data, apply a hash function to the decrypted data to obtain a hash value of the decrypted data, then decrypt the data signature through the temporary symmetric key to obtain a hash value, and perform a consistency match between the hash value and the hash value of the decrypted data. If the two hash values are the same, perform a data printing operation; if the two hash values are different, generate a data tampering alarm signal.
[0029] When the printing device terminal receives a high-importance data packet, it decrypts the encrypted symmetric key using the public key to generate a temporary symmetric key. It decrypts the ciphertext data using the temporary symmetric key to obtain the decrypted data, applies a hash function to the decrypted data to obtain the hash value of the decrypted data. Subsequently, it decrypts the data signature using the temporary symmetric key to obtain the hash value, and performs a consistency match between the said hash value and the hash value of the decrypted data. If the two hash values are consistent, it performs a data printing operation. If the two hash values are inconsistent, it generates a data tampering alarm signal.
[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0031] 1. Abnormal behavior monitoring: By constructing a printing behavior prediction model and performing a similarity match between the actual printing behavior data time series and the predicted sequence, abnormal printing behaviors can be detected in a timely manner. If the printing behavior similarity is lower than the threshold, not only the printing task is rejected, but also an alarm signal is generated, effectively preventing illegal printing operations and avoiding the leakage of confidential data due to abnormal printing behaviors.
[0032] 2. Hierarchical encryption: Different levels of encryption are performed according to the importance level of the printing task. For high-importance level tasks, an asymmetric encryption algorithm is used to generate a key pair, combined with a symmetric encryption algorithm, and the private key is used to encrypt the temporary symmetric key to ensure the security of key transmission; for low-importance level tasks, a symmetric encryption algorithm is used to generate a temporary symmetric key to encrypt the data. This hierarchical encryption method reasonably allocates computing resources while ensuring data security and improves encryption efficiency.
[0033] 3. Data integrity verification: Whether it is a high-importance or low-importance data packet, a hash value is generated through a hash function and encrypted to form a digital signature, and a consistency match is performed at the receiving end. If the hash values are inconsistent, a data tampering alarm signal is generated, ensuring the integrity of the printed data during transmission and preventing the data from being maliciously tampered with.
[0034] 4. Communication security guarantee: A preset network security protocol is used to build an encrypted communication channel between the user device terminal and the printing device terminal, preventing the data from being stolen or tampered with during transmission, and further enhancing the security of data transmission.
[0035] 5. Data management and analysis: A log database is constructed to store the log information between the user device terminal and the printing device terminal, providing data support for printing behavior analysis. On the one hand, it helps to improve the printing behavior prediction model, enabling it to more accurately predict normal printing behaviors, thereby improving the accuracy of anomaly detection; on the other hand, it can be used for auditing and traceability, facilitating the identification of the cause in case of security issues.
[0036] 6. Adaptability and Flexibility: The printing behavior prediction model of deep learning can be trained and optimized based on continuously updated log data to adapt to changes in different users and printing scenarios. At the same time, the hierarchical encryption method can flexibly adjust the encryption strategy according to the importance of the printing task to meet diverse security requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Figure 1 It is a schematic diagram of a method for encrypting and protecting printing data for a printing device according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0038] Next, with reference to the accompanying drawings in the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.
[0039] As Figure 1 shown, a method for encrypting and protecting printing data for a printing device includes the following steps:
[0040] Step S1: Construct a printing behavior prediction model. When a printing task is sent from the user device end to the printing device end, perform similarity matching between the time series of printing behavior data between the user device end and the printing device end and the predicted time series of printing behavior data output by the printing behavior prediction model.
[0041] Step S2: When the similarity matching result allows the user device end to send the printing task, obtain the digest information of the printing task, obtain the importance level corresponding to the printing task according to the digest information, and perform high-importance encryption or low-importance encryption of the printing data according to the importance level corresponding to the printing task.
[0042] Step S3: Decrypt the data packet received by the printing device terminal, and perform data printing operations or generate a data tampering alarm signal according to the decryption result.
[0043] It should be further noted that, in the specific implementation process, a preset network security protocol (such as the SSL / TLS protocol, etc.) is set, an encrypted communication channel is constructed between several user device ends and the printing device end according to the network security protocol, and a log database is constructed, and the log database is used to store the log information between the user device end and the printing device end.
[0044] It should be further noted that, in the specific implementation process, the process of constructing the printing behavior prediction model includes:
[0045] Build a printing behavior prediction model based on deep learning, extract features from the log information in the log database, and obtain the time series of printing behavior data. The time series of printing behavior data includes various types of behavior metrics as follows: creation time, sending time, receiving time, decryption time, printing start time, printing end time, summary information of printing data, user identity information, encryption algorithm used, and key information. Use the printing data as the training set and the test set, input the training set into the printing behavior prediction model for training until the loss function is trained stably, save the model parameters, test the printing behavior prediction model through the test set until it meets the preset requirements, and output the printing behavior prediction model.
[0046] Building a printing behavior prediction model based on deep learning is a complex process that involves multiple steps such as model selection, training, validation, and testing. The following is a detailed supplementary description of this process:
[0047] In the present invention, a recurrent neural network (RNN) suitable for time series analysis is selected as the deep learning architecture. After determining the model architecture, the mean squared error (MSE) is selected as the optimization objective, and then the prepared training set is input into the selected deep learning model to start training. During the training process, the weights are continuously updated through the backpropagation algorithm, making the loss function gradually decrease until it reaches a stable state. During this period, techniques such as early stopping are used to avoid overfitting. In addition to the basic training process, the various parameters of the model are tuned through grid search. The parameters include learning rate, batch size, regularization coefficient, etc.
[0048] When the model training is completed and the parameters are adjusted, the final evaluation is carried out through the test set to obtain the evaluation results of the model. The evaluation results include classification metrics such as accuracy, recall rate, and F1 score. According to the evaluation results on the test set, it is judged whether the model meets the expected standards. If the requirements are met, the model parameters are saved and ready for deployment; if not, it is necessary to return to a previous stage to re-examine issues such as data quality, model structure, or training strategy.
[0049] It should be further noted that in the specific implementation process, when the user device sends a printing task to the printing device, the process of performing similarity matching between the time series of printing behavior data between the user device and the printing device and the predicted time series of printing behavior data output by the printing behavior prediction model includes:
[0050] A preset collection period, with the collection period being one day. Obtain the log information between the user device side and the printing device side during the current collection period, extract features from the log information, obtain the time series of printing behavior data between the user device side and the printing device side, and according to the printing behavior prediction model, output the predicted time series of printing behavior data between the user device side and the printing device side during the current collection period;
[0051] Perform similarity matching between the time series of printing behavior data between the user device side and the printing device side and the corresponding predicted time series of printing behavior data to obtain the printing behavior similarity. Compare the printing behavior similarity with the preset printing behavior similarity threshold. If the printing behavior similarity is greater than or equal to the printing similarity threshold, allow the user device side to send a printing task to the printing device side;
[0052] Among them, the calculation formula for obtaining the printing behavior similarity is:
[0053]
[0054] Among them, ds represents the printing behavior similarity, D iqt represents the value of the behavior index q at the t-th moment in the time series of printing behavior data, D jqt represents the value of the behavior index q at the t-th moment in the predicted time series of printing behavior data, n1 represents the total number of behavior indexes, and n2 represents the total number of moments within the collection period;
[0055] If the printing behavior similarity is less than the printing similarity threshold, reject the printing task sent by the user device side to the printing device side, generate a printing behavior anomaly alarm signal, send the printing behavior anomaly alarm signal to the administrator or user by means of email, text message or system pop-up window, and record the detailed information of the abnormal event for subsequent security analysis and processing.
[0056] It should be further noted that in the specific implementation process, the process of obtaining the summary information of the printing task, obtaining the importance level corresponding to the printing task according to the summary information, and performing high-importance encryption or low-importance encryption of the printing data according to the importance level corresponding to the printing task includes:
[0057] When allowing the user device side to send a printing task, extract the summary information of the printing task to obtain the summary information of the printing task. Preset the importance levels corresponding to different summary information, where the importance levels include high-importance level and low-importance level, and obtain the importance level corresponding to the printing task;
[0058] If the importance level corresponding to the printing task is the high importance level, high-importance encryption of the printing data is performed. If the importance level corresponding to the printing task is the low importance level, low-importance encryption of the printing data is performed.
[0059] It should be further noted that in the specific implementation process, the process of performing low-importance encryption of the printing data includes:
[0060] Using a symmetric encryption algorithm, the user device generates a temporary symmetric key, uses the temporary symmetric key to encrypt the printing task to generate ciphertext printing data, applies a hash function to the ciphertext printing data to generate a hash value of the ciphertext printing data, uses the temporary symmetric key to encrypt the hash value of the ciphertext printing data to generate a digital signature of the ciphertext printing data, packs the ciphertext printing data, the digital signature, and the temporary symmetric key into a data packet, marks the data packet as a low-importance data packet, and sends it to the printing device terminal.
[0061] It should be further noted that in the specific implementation process, the process of performing high-importance encryption of the printing data includes:
[0062] Previously, use an asymmetric encryption algorithm to generate an asymmetric key pair for the user device. The asymmetric key pair includes a public key and a private key, and use a symmetric encryption algorithm to generate a temporary symmetric key for the user device. Encrypt the printing task through the temporary symmetric key to generate ciphertext printing data, apply a hash function to the ciphertext printing data to generate a hash value of the ciphertext printing data, use the temporary symmetric key to encrypt the hash value of the ciphertext printing data to generate a digital signature of the ciphertext printing data, encrypt the temporary symmetric key through the private key to generate an encrypted symmetric key, pack the ciphertext printing data, the encrypted symmetric key, and the digital signature into a data packet, and mark the data packet as a high-importance data packet and send it to the printing device terminal.
[0063] It should be further noted that in the specific implementation process, the process of decrypting the data packet received by the printing device terminal and performing data printing operations or generating a data tampering alarm signal according to the decryption result includes:
[0064] When the printing device terminal receives a low-importance data packet, decrypt the ciphertext data through the temporary symmetric key to obtain the decrypted data, apply a hash function to the decrypted data to obtain the hash value of the decrypted data, then decrypt the data signature through the temporary symmetric key to obtain the hash value, and perform a consistency match between the hash value and the hash value of the decrypted data. If the two hash values are the same, perform a data printing operation. If the two hash values are different, generate a data tampering alarm signal;
[0065] When the printing device terminal receives a high-importance data packet, it decrypts the encrypted symmetric key using the public key to generate a temporary symmetric key. It then decrypts the ciphertext data using the temporary symmetric key to obtain the decrypted data, applies a hash function to the decrypted data to obtain the hash value of the decrypted data. Subsequently, it decrypts the data signature using the temporary symmetric key to obtain the hash value, and performs a consistency match between the obtained hash value and the hash value of the decrypted data. If the two hash values are consistent, it performs a data printing operation; if the two hash values are inconsistent, it generates a data tampering alarm signal.
[0066] The above embodiments are only used to illustrate the technical method of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical method of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical method of the present invention.
Claims
1. A printing data encryption protection method for a printing device, characterized in that: The following steps are involved: Step s1: construct a printing behavior prediction model. When the user device sends a printing task to the printing device, the printing behavior data timing sequence between the user device and the printing device is matched with the estimated printing behavior data timing sequence output by the printing behavior prediction model for similarity; Step s2: when the similarity matching result is to allow the user device to send the print task, obtain summary information of the print task, obtain the importance level corresponding to the print task according to the summary information, and perform high-importance encryption of the print data or low-importance encryption of the print data according to the importance level corresponding to the print task; Step s3: decrypt the data packet received by the printing device terminal, and perform data printing operation or generate a data tampering alarm signal according to the decryption result.
2. A printing data encryption protection method for a printing device according to claim 1, characterized in that: A network security protocol is preset, an encrypted communication channel is constructed between a plurality of user device ends and a printing device end according to the network security protocol, and a log database is constructed, wherein the log database is used to store log information between the user device ends and the printing device ends.
3. A printing data encryption protection method for a printing device according to claim 2, characterized in that: The process of building a printing behavior prediction model includes: A printing behavior prediction model is constructed based on deep learning, and features are extracted from the log information in the log database to obtain a time series of printing behavior data. The printing data is used as a training set and a test set, and the training set is input into the printing behavior prediction model for training until the loss function training is stable. The model parameters are saved, and the printing behavior prediction model is tested by the test set until it meets the preset requirements, and the printing behavior prediction model is output.
4. The method for encrypting and protecting printing data for a printing device according to claim 3, characterized in that: When the user device sends a print task to the printing device, the process of performing similarity matching between the printing behavior data timing sequence between the user device and the printing device and the estimated printing behavior data timing sequence output by the printing behavior prediction model includes: Preset a collection cycle, obtain log information between the user device and the printing device in the current collection cycle, extract features from the log information, obtain a time series sequence of printing behavior data between the user device and the printing device, and output an estimated time series sequence of printing behavior data between the user device and the printing device in the current collection cycle according to a printing behavior estimation model; Perform similarity matching between the printing behavior data timing sequence between the user device and the printing device and the corresponding estimated printing behavior data timing sequence to obtain printing behavior similarity, compare the printing behavior similarity with a preset printing behavior similarity threshold, and if the printing behavior similarity is greater than or equal to the printing similarity threshold, allow the user device to send a printing task to the printing device; If the printing behavior similarity is less than the printing similarity threshold, the user device side is rejected from sending the printing task to the printing device side, and a printing behavior abnormality alarm signal is generated.
5. The method for encrypting and protecting printing data for a printing device according to claim 4, characterized in that: The process of obtaining summary information of the print task, obtaining the importance level corresponding to the print task according to the summary information, and performing high-importance encryption of the print data or low-importance encryption of the print data according to the importance level corresponding to the print task includes: When the user device is allowed to send a print task, extract summary information of the print task, obtain summary information of the print task, preset importance levels corresponding to different summary information, the importance levels include high importance level and low importance level, and obtain the importance level corresponding to the print task; If the importance level corresponding to the print task is a high importance level, the print data is encrypted with high importance; if the importance level corresponding to the print task is a low importance level, the print data is encrypted with low importance.
6. A printing data encryption protection method for a printing device according to claim 5, characterized in that: The process of low-importance encryption of print data includes: A symmetric encryption algorithm is used to generate a temporary symmetric key on the user device side, the temporary symmetric key is used to encrypt the data of the print task, the ciphertext print data is generated, a hash function is applied to the ciphertext print data, a hash value of the ciphertext print data is generated, the hash value of the ciphertext print data is encrypted using the temporary symmetric key, a digital signature of the ciphertext print data is generated, the ciphertext print data, the digital signature and the temporary symmetric key are packaged into a data packet, the data packet is marked as a low-importance data packet and sent to the printing device terminal.
7. The method for encrypting and protecting printing data for a printing device according to claim 6, characterized in that: The process of high-importance encryption of print data includes: An asymmetric key pair is generated in advance at the user device end using an asymmetric encryption algorithm, wherein the asymmetric key pair includes a public key and a private key, and a temporary symmetric key is generated at the user device end using a symmetric encryption algorithm, data of the print task is encrypted using the temporary symmetric key, ciphertext print data is generated, a hash function is applied to the ciphertext print data, a hash value of the ciphertext print data is generated, the hash value of the ciphertext print data is encrypted using the temporary symmetric key, a digital signature of the ciphertext print data is generated, the temporary symmetric key is encrypted using the private key, an encrypted symmetric key is generated, the ciphertext print data, the encrypted symmetric key and the digital signature are packaged into a data packet, the data packet is marked as a high-importance data packet and sent to the printing device terminal.
8. The method for encrypting and protecting printing data for a printing device according to claim 7, characterized in that: The process of decrypting the data packet received by the printing device terminal and performing data printing operation or generating a data tampering alarm signal according to the decryption result includes: When the printing device terminal receives a low-importance data packet, the ciphertext data is decrypted by using a temporary symmetric key to obtain decrypted data, and a hash function is applied to the decrypted data to obtain a hash value of the decrypted data. Subsequently, the data signature is decrypted by using the temporary symmetric key to obtain a hash value, and the hash value is matched with the hash value of the decrypted data for consistency. If the hash values of the two are consistent, a data printing operation is performed. If the hash values of the two are inconsistent, a data tampering alarm signal is generated. When the printing device terminal receives a high-importance data packet, the encrypted symmetric key is decrypted by the public key to generate a temporary symmetric key, the ciphertext data is decrypted by the temporary symmetric key to obtain the decrypted data, and the hash function is applied to the decrypted data to obtain the hash value of the decrypted data. The data signature is then decrypted by the temporary symmetric key to obtain the hash value, and the hash value is matched with the hash value of the decrypted data. If the hash values are consistent, the data printing operation is performed. If the hash values are inconsistent, a data tampering alarm signal is generated.